First of all, please rest assured that your money is completely safe - you will always receive either the in-game items you bought or a refund for the purchase if it doesn't go through.
While rare, delays in payment processing may happen. If your purchase didn't go through right away, wait for a couple of hours - the items will most likely be credited to your account within this period.
If this doesn't happen, please send us a support request indicating the date and time (including the time zone) of the purchase, and we will figure it out.